The invention relates to a device and a method for determining the position of a first shaft and of a second shaft that is joined to the first shaft by means of a coupling, with respect to each other, having a first measurement unit being placed on a circumferential surface of the first shaft and a second measurement unit being placed on a circumferential surface of the second shaft. At least one of the two measurement units has means for producing at least one light beam bundle, and at least one of the two measurement units has detection means for detecting data relating to the impingement position of the light beam bundle on at least one detection area. Furthermore, at least one of the two measurement units is provided with at least one sensor for detecting the angle of rotation of the shaft. The parallel offset as well as the horizontal or vertical angular offset of the two shafts can be determined from the impingement positions of the light beam bundle determined in a plurality of measured positions, that is, in a plurality of angle-of-rotation positions, this being performed typically by curve fitting.
An overview of such shaft alignment measurement devices may be found in U.S. Pat. No. 6,434,849 B1, for example, with a data analysis by means of curve fitting to an ellipse also being described.
Described in DE 33 20 163 A1 and DE 39 11 307 A1 are shaft alignment measurement devices in which the first measurement unit emits a light beam, which is reflected back by a mirror prism of the second measurement unit onto a biaxial optical detector of the first measurement unit.
Known from DE 38 14 466 A1 is a shaft alignment measurement device in which the first measurement unit emits a light beam, which impinges on two biaxial optical detectors of the second measurement unit that are arranged in optical succession in the axial direction.
Described in DE 33 35 336 A1 is a shaft alignment measurement device in which both the first and the second measurement unit each emit a light beam and have a biaxial optical detector, with the light beam being directed in each case onto the detector of the other measurement unit. A shaft alignment measurement device operating according to this principle is also described in U.S. Pat. No. 6,873,931 B1, whereby the two measurement units are each provided with two biaxial acceleration sensors for automatically detecting the angle of rotation of the shaft.
Described in EP 2 093 537 A1 is a measurement device in which the first measurement unit emits a fanned light beam, which impinges on two optical strip detectors of the second measurement unit, these detectors being arranged with a lateral spacing parallel to each other, with the longitudinal direction of the detectors being arranged perpendicular to the fan plane of the light beam; not only the determination of the alignment of the shafts with respect to each other but also the determination of the coupling play is described.
Known from WO 2010/042309 A1 is a shaft alignment measurement device in which each of the two measurement units is provided with a camera arranged in a housing, with the side of the housing facing the other unit being provided with an optical pattern that is recorded by the opposite-lying camera. Here, the side of the housing provided with the pattern is provided with an aperture in each case, through which the opposite-lying pattern is imaged. In an alternative embodiment, one of the two units is provided only with a camera, but not with a pattern, whereas the other unit has no camera, but is provided with a three-dimensional pattern.
Described in EP 1 211 480 A2 is a shaft alignment measurement device in which the first measurement unit is provided with a light source, which directs a light beam onto the second measurement unit provided with a matte screen; the side of the matte screen facing away from the first measurement unit is imaged on an image detector, likewise constituting a part of the second measurement unit, by means of appropriate optics.
Described in U.S. Pat. No. 6,981,333 B2 is how vibrations that occur during measurement are determined by means of gyroscopic sensors when the alignment of shafts is measured, so as to prevent insofar as possible any erroneous readings of the alignment measurement owing to such vibrations.
Described in U.S. Pat. No. 5,980,094 is a shaft alignment measurement method in which, as in DE 33 35 336 A1, the two measurement units direct a light beam onto a biaxial optical detector of the other respective measurement unit, with the radial component of the point of impingement of the light beam being plotted versus the angle of rotation for analysis of the data for each of the two detectors and a sine curve being fitted to the measurement data in each case. In this case, a confidence factor, based on the number of measured points and the angular distribution of the measured points, is determined for the set of data that is being determined and analyzed. It is further proposed in this case to eliminate suspicious data points from the determined set of data either manually or automatically, with a new curve fitting then being performed on the basis of the set of data that has been reduced in this manner and with it being checked whether the confidence factor has increased owing to the reduction in the set of data. However, it is not mentioned how the suspicious data points can be identified, apart from the confidence factor being increased through elimination of these suspicious data points. A similar alignment method is described in U.S. Pat. No. 5,263,261.